1) ignore all other apps that might have 'gotten away with it'. If you want, try to get away with it yourself. But pointing out that your older brother got to do something is only going to get your older brother in trouble.
2) "Basically we connect buyers and sellers and allow video call through the app( like consultation service)" - the component that is facilitated within the app, i.e. the connection between a buyer and a seller as determined by some database or whatever within the app is subject to the 11.2 requirement that you use IAP. But the video call with a real world person would allow you to use 11.3 to avoid IAP if it were not in the app. But then you do it within the app. So you can divide up your 'value/price' into three components - connect a buyer to a seller, present the buyer for a conversation with the expert seller, the actual video link. The first is IAP, the second is not to the extent that you are paying for the services of the expert buyer, the third may or may not be. I recall intense discussions on whether VOIP minutes had to be paid by IAP or couldn't be paid by IAP - I believe it was decided that it could go either way but I am not sure on that. So, IMHO, bottom line is if you are actually paying most of the fee for a consultant expert buyer you cannot use IAP but if you are not paying for the consultant expert buyer then you are just selling stuff facilitated by the App and have to use IAP. I would chose what you want to have happen, use the content within this #2 to justify it and proceed under #1 above.